Hydrocarbon conversion



E. H. MCGREW HYDROCARBON CONVERSION Filed Aug. 21, 1939 June 30, 1942.

R0 MSNM@ Patented June 30, 1942 mmRocAmsoN coNvEasxoN Edwin H. McGrew, Chicago, lll., assignor to Universal Oil Products Company, Chicago, Ill., a

corporation of Delaware Application August 21, 1939, Serial No. 291,193

(ci. 19e-sz) 2 Claims.

This invention relates to a process for converting hydrocarbon oils into substantial yields of gasoline of high octane rating, relatively low olefin content, yand a low potential gum content. More specically, it relates to a process which involves a series of concomitant steps combined in a novel and advantageous manner so that they cooperate to produce the desired results.

The invention involves principally thermal cracking treatment of a heavy hydrocarbon oil, such as, for example, reduced crude, high temperature catalytic cracking treatment of a lighter hydrocarbon oil, such as gas-oil, low temperature catalytic cracking treatment of the gasolines produced in thethermal cracking and the high temperature catalytic cracking treatments in commingled state with light reux condensate formed in the thermal cracking treatment to produce a gasoline of high octane rating and relatively low olefin content.

The term high temperature catalytic cracking treatment as used throughout the specification and claims refers to the treatment of hydrocargasolines cannot be used as an aviation fuel.

tiesand because the gasolines that contain high percentages of oleflnic hydrocarbons have a relatively high acid heat test and a relatively low susceptibility to added antiknockng agents, these On the other hand, gasolines which are predominantly parainic and which may also contain aromatic hydrocarbons, and which, in addition, contain relatively large amounts of isomeric parainic compounds, are particularly useful as an aviation gasoline because of the low acid heat test and good susceptibility to added antiknocking bon oils in the presence of catalytically active masses at temperatures ranging, for example from 800 to 1200 F. and at pressures varying from substantially atmospheric to 200 pounds or more per square inch whereby to effect substantial conversion to gasoline boiling range hydrocarbons. The term low temperature cracking treatment, on the other hand, refers to the treatment of gasoline boiling range hydrocarbons at relatively low temperatures, in a more limited sense, however, it refers to the treatment of gasoline boiling range hydrocarbons in commingled state with light recycle formed in the thermal cracking'treatment in the presence of catalytically active masses of a similar character to those employed in the high temperature catalytic cracking treatment at temperatures ranging, for example, from 600 to 900 F. and at a pressure ranging from substantially atmospheric to 200 pounds or more per square inch whereby to effect a transfer of hydrogen agents, such as tetraethyl le'ad. It has been found that when the gasolinas produced in thermal.

agents.

It is believed that in the low temperature catalytic cracking treatment that saturated hydrocarbons, and particularly the naphthenic hydrocarbons of the recycle oils act as hydrogen donors for the oleflnic hydrocarbons of the gasoline, whereby the oleiinic hydrocarbons become saturated to form parailinic hydrocarbons and naphthenic hydrocarbons are 'converted to aromatic hydrocarbons. Various other reactions, such as, for example, dehydrogenation and cyclcizationr of an aliphatic hydrocarbon to form an 'aromatic hydrocarbon with the formation of 2 to 3 molecules of hydrogen which attach to the unreacted ol'flnic hydrocarbons may also take place. However, since the invention is concerned primarily with a process in which the various reactions may be conducted, no further discussion is necessary of what chemical reaction may possibly be involved in the low temperature catalytic cracking porous conversion products from non-vaporous liquid residue,- recovering the latter, fractionating said vaporous conversion products to form light and heavyy reflux condensate and to separate fractionated vapors boiling in the range of'gasoline, returning said heavy reflux condensate to the thermal cracking treatment, simultaneously commingling reflux condensates formed ina high temperature' catalytic cracking treatment and in a subsequent low temperature cracking treatment with a light hydrocarbon oil, heating and .vaporizing the mixture and subjecting the heated vapors to contact with a cracking catalyst in a high temperature cracking zone, fractionating the conversion products from said high temperature cracking zone to separate gasoline boiling range hydrocarbons from the higher boiling hydrocarbons, condensing the latter as reflux condensate and supplying it as aforesaid to the high temperature catalytic cracking treatment, subjecting said gasoline boiling range hydrocarbons to cooling and condensation and collecting the resulting distillate and gas, commingling the fractionated vapors from the thermal cracking treatment and the distillate from the high temperature catalytic cracking treatment with light reflux condensate from the thermal cracking treatment, heating `the mixture and subjecting the heated oil to contact with a cracking catalyst in a low temperature cracking treatment, fractionating the conversion products from the low temperature cracking treatment to separate a gasoline product from the higher boiling hydrocarbons, recovering the former, condensing said higher boiling hydrocarbons as reflux condenf sate and returning it to the high temperature catalytic cracking treatment.

The accompanying diagrammatic drawing shows in conventional side elevation one specific form of the apparatus in which the object of the invention may be accomplished. It is to be understood that the invention isnot limited to processing in the specific form of the apparatus herein disclosed and that various modifications of the process and apparatus herein described may be made withoutdeparting from the broad scope of the invention.

Referring now to the drawing, charging stock, preferably comprising a heavy hydrocarbon oil, such as, for example, reduced crude, is introduced through line I and valve 2 to pump 3, which discharges through line 4 and valve 5, the oil commingled with heavy reflux condensate, formed as herein described, and the mixture introduced to heating coil 6. The oil in passing through heating coil 6 is raised to the desired cracking temperature, which may range, for example, from 850 to 1000 F., and is maintained at this temperature for a sufficient period of time for substantial cracking to be effected, theheat for cracking being supplied by furnace 1. The heated conversion products leaving heating coil 8, at a superatmospheric pressure ranging, for example, from 200 to 600 pounds or more per square inch, are directed through line 8 and valve 9 into reaction chamber I0 wherein they are subjected to prolonged conversion atv an elevated temperature. Reaction chamber III is preferably operated at a superatmospheric pressure substantially the same as that employed on the outlet The vaporous and liquid conversion products leaving reaction chamber I are directed through line II and valve I2 into vaporizing and separating chamber I3, which is operated at a substantially reduced pressure relative to that employed in reaction chamber I Il, ranging, for example, from 50 to 250 pounds or more per square inch wherein the vaporous conversionv products are separated and the liquid conversion products subjected to substantial further vaporization to form a non-vaporous liquid residue.

Valve I2 is preferably a pressure control valve by 4means of which a substantial superatmospheric pressure is maintained on the heating coil and communicating reaction chamber after which the pressure is lowered to effect vaporization in chamber I3. The non-vaporous liquid residue separated in chamber I3 is directed from the lower portion thereof through line I4 and valve I5 to cooling and storage or elsewhere as desired The vaporous conversion products, together with the vapors evolved within chamber I3, are directed-through line I8 and valve I'I into fractionator I8, which is preferably operated at a superatmospheric pressure of substantially the same magnitude as that employed in chamber I3. The vaporous products introduced to fractionator I8 are subjected to fractionation therein to form light and heavy reflux condensates and to sepa'- rate fractionated vapors boiling in the range of gasoline. The heavy reflux condensate is dlrected from the lower portion of fractionator I8 through line I9 and valve 20 into pump 2| which discharges through line 22 and valve 23 into line 4 where ythe heavy reflux condensate commingles with the charging stock, as previously described.

Fractionated vapors separated in fractionator I8 are directed from the upper portion thereof through line 24, and, when desired, all of the vapors may be directed through valve 25 into cooler and condenser 28 wherein they are subjected to cooling and condensation. The distillate formed in condenser 28, together with undissolved and uncondensed normally gaseous hydrocarbons, is directed through line 21 and valve 28 into receiver 29 wherein the distillate and gases are collected and separated. Normally gaseous hydrocarbons collected in the upper portion of receiver 29 are directed therefrom through line 30 and valve 3| to collection and storage or to further treatment as desired. A portion of the distillate collected in receiver 29 may be returned to the upper portion of fractionator I8,

by well known means not shown, as a refluxing and cooling medium therein. When desired, the balance of the distillate may be directed through line 32 and valve 33 and recovered as a product of the process. On the other hand, the distillate collected in receiver 29 may, when desired, be directed through line 34 and valve 35 to pump 36, which discharges through line 31 and valve 38 into line 82 for low temperature catalytic condensation when the thermally cracked gaso.

line is subjected to low temperature catalytic cracking treatment. In this case, the portion of fractionated vapors in line 24, which is in excess of the amount requiredl for refluxing the upper portion of fractionator I8, may be directed in the high temperature and low temperature catalytic cracking reactions, as hereinafter described, and/themixture thereafter introduced toheating coil 46. The oil in passing through heating coil 46 is'substantially completely vaporized therein and raised to the desired temperature, which may range, for example, from 800 to 1200 F. without substantial pyrolytic `cracking thereof, the heat being furnished by furnace 41. 'Ilie heated vapors leaving heating coll 46 at a .pressure ranging, vfor example, from substantially atmospheric to 200 pounds or more per square inch, are directed through line 48 and valve 49 into reactor 50 wherein the vapors are subjected to contact with a cracking catalyst disposed therein while they are maintained at substantially the same temperature as that employed on the outlet of the heating coil by means of heat supplied from an external source whereby to eiect substantial conversion into gasoline boiling range hydrocarbons.

The preferred cracking catalysts for use in the present process consist in general of a precipitated alumina hydrogel and/or zirconia hydrogel composited with silica hydrogel, the gel composite being washed, dried, formed into particles and calcined to produce a catalytic mass. It is not intended, however, that the process should be limited to these particular catalysts, for other catalysts, such as, for example, the hydrosilicates of alumina, acid treated clays, and the like, may be used within the broad scope of the invention.

In the following specification and claims the terms silica, alumina, silica-zirconia, and silicaalumina-zirconia masses are used in the broad sense to designate the synthetic composites referred to above. The preferred catalysts may be prepared by precipitating silica from a solution as a hydrogel within or upon which the alumina and/or zirconia are deposited also by precipitation as hydrogels. The silica hydrogel may conveniently be prepared by acidifying an aqueous solution of sodium silicate by the addition of a required amount ofhydrochloric acid. After precipitating, the silica gel is preferably washed until substantially free from alkali metal salts. The washed silica hydrogel is then suspendedin a solution of alumina and/or zirconium salts and an alkaline precipitant, such as ammonium hydroxide, ammonium carbonite or ammonium sulfide added to the solution to precipitate ploys-a plurality of relatively small diameter reactor tubes containing; the desired catalyst, the tubes being coniined within an enclosed zone to which heat from an external source may be supplied for the purpose of maintaining the reactants at the desired temperature during the conversion reaction. In addition, since relatively short periods of operation are employed in catalytic cracking because of -the rather rapid deposition of carbon upon the surface and within the pores of the catalystparticles which'necessitates frequent reactivation, it is preferred that a plurality of reactors be employed, although only one is shown in the drawing, in order that one or moremay be segregated and the catalysts disposed therein subjected to reactivation'while conversion of the hydrocarbon vapors is being accomplished in the other or others. Suitable means, not shown,may be employed for reactivating the catalyst disposed within the various reactors during the period those particular reacthe balance for the purarating zone 54, which forms the lower portion aluminum and/or zirconium hydrogels. The final proximate range of 1000 to 1500 F. Various other procedures, such as, for example, coprecipitation of the hydrated gels may be employed, wheny desired, to produce the preferred catalyst.

Reactor I0 is preferably of the type which emof fractionator and separator 53 which is operated at a superatmospheric pressure substantially the same as that employed on the outlet of reactor 50, wherein the vaporous conversion products are separated from the non-vaporous liquid residue. 'I'he non-vaporous liquid residue is removed from this zone through line 55 and valve 56 and recovered as a product of the process. The vaporous conversion products are directed through separating tray 51 into fraction- 'ating zone 58 where they undergo fractionation to form reiiux condensate and to separate gasoline boiling range hydrocarbons. The reflux condensate formed in fractionating zone '58 is directed therefrom through line.59 and valve 60 to pump 6I, which discharges through line 62 and valve 63 into line 44, wherein the reux condensate commingles with the light oil, as previously described.

The gasoline boiling range hydrocarbons separated in fractlonating zone 58 are directed in the vapor state from the upper portion thereof through line 64 andvalve 65 into cooler and condenser 66 where they are subjected to cooling and condensation. The resulting distillate, together with undissolved and uncondensed Anormally gaseous hydrocarbons leaving condenser 66, is directed through line 61 and valve 68 into receiver 69 wherein the distillate and gas is collected and separated. The normally gaseoushydrocarbons collected in the upper portion of receiver 69 are directed therefrom through line 10 and valve 1I -to storage or to further treatment as desired. A portion of the distillate collected in receiver 69 may be returned to the upper portion of fractlonating zone 58, by Well known means not shown, as a reiiuxing and cooling medium. The balance of the distillate may, when desired, be recovered as a product of the high temperature cracking treatment to low temperature catalytic cracking treatment, in which case the distillate collected in receiver 89 is directed through line 18 and valve 15 to pump 16, which discharges through line 11 and valve 18 into line 82, the distillate thereafter being subjected to treatment as subsequently described.

Light reflux condensate formed in fractionator 8 is directed through line 19 and valve 88 to pump 8|, which discharges through line 82 and valve 83. Reflux condensate in line 82 commingles with either the fractionated vapors or distillate from the thermal cracking treatment and/or the distillate from the high temperature catalytic cracking treatment after Lwhich the mixture is introduced to heating coil 88. The oil introduced to heating coil 88 is raised to a temperature in the range of 600 to 900 F. without substantial pyrolytic .cracking thereof by means of heat supplied from furnace 88. The heated oil leaving heating coil 88 at a pressure ranging, for example, from substantially atmospheric to 200 pounds or more per square'inch is directed through line 88 and valve 81 into reactor 89 wherein it is subjected to contact' with a cracking catalyst while maintaining the oil at substantially the same temperature as that employed on the outlet of heating coil 88. -The catalyst employed in reactor 89 may be of the same composition as that employed and described in connection with reactor 88. 'I'he low and high temperature cracking reactions differ essentially with respect to temperature and contact times employed, the reaction in reactor 58 being carried out at a relatively high temperature and short contact time, whereas the reaction in reactor 89 is carried out at a lower temperature and at a longer contact time. Reactors 58 and 89 may be of essentially the same design, however, as was previously mentioned, various other types of reactors may be employed to accomplish the desired results.

'I'he conversion products leaving reactor 89 are directed throimh line 98 and valve 9| into fractionator 92, maintained at substantially the same or at a relatively reduced pressure relative to that employed on the outlet of reactor 89, wherein fractionated vapors boiling in the range of gasoline are separated from the higher boiling hydrocarbons, the latter being condensed as reflux condensate in the fractionating zone. The reflux condensate is removed from fractionator 92 and in receiver |88 is removed therefrom through line |88 and valve |81 and recovered as a product of the process.

As an example of one specific operation of the process as it may be conducted in an apparatus such as illustrated and above described to accomplish the desired results is approximately as follows: Y

A Mid-Continent reduced crude oil, having a 25 A. P. I. gravity, was commingled with heavy reflux condensate formed in the thermal cracking treatment and the mixture subjected to thermal cracking treatment in a'heating coll and communicating reaction chamber operated at a temperature of 930 F. and a superatmospheric pressure of 250 pounds per square inch. The vaporous and liquid conversion products leaving the reaction chamber were introduced to the vaporizlng and separating chamber operated at a superatmospheric pressure of '15 pounds per square inch, the vaporous conversion products separated from the non-vaporous liquid residue, and the latter recovered as a productv of the process. The vaporous conversion products were subjected to fractionation at a superatmospheric 'pressure substantially the same as that employed in the vaporizing and separating chamber to form light is directed through line 98 and valve 98 into pump 95, which discharges through line 98 and valve 91 into line 82 wherein the reflux condensate from this operation commingles with the reflux condensate from the high temperature cracking treatment and this mixture thereafter |08, is directed through line |8| and valve |82 into receiver |83 wherein the distillate and gas is collected and separated. The normally gasenus hydrocarbons collected in receiver |83 are directed from the upper portion thereof through line |88 and valve |85 and recovered as a product of the process. Distillate collected and separated and heavy reflux condensate and to separate gasoline boiling range hydrocarbons having an end boiling point of 400 F. The heavy reflux condensate was returned to the thermal cracking treatment.

The fractionated vapors from the thermal cracking treatment and the distillate formed in the high temperature catalytic cracking treatment, as hereinafter described, were commingled with the light reux condensate from the thermal cracking treatment and the mixture heated to a temperature of '150 F. and passed over a silicaalumina-zirconia catalyst at a superatmospheric pressure of pounds per square inch and a liquid space velocity of 1 in a low temperature cracking zone. The conversion products from the low temperature cracking zone were subjected to fractionation to separate fractionated vapors having an end boiling point of 300 F. from the higher boiling hydrocarbons. The fractionated vapors were subjected to cooling and condensation and the resulting distillate and gases collected and separated and recovered as products .of the process.

The hydrocarbons, heavier than gasoline, sep- -arated in the fractionating zone following the low temperature cracking zone, were condensed as reflux condensate. 'I'his reflux condensate was commingled with renux condensate produced in the high temperature catalytic cracking treatment and with a Mid-Continent gas-oil of 36 A. P. I. gravity. This mixture was vaporized and heated to a temperature of 940 F. and subject- -ed to contact with a silica-alumina-zirconia catalyst at a superatmospheric pressure of 60 pounds per square inch and at a liquid space velocity of 4. The conversion products from this treatment were introduced to a separating zone wherein the vaporous conversion products were separated from the non-vaporous liquid residue and the latter recovered as a product of the process. The vaporous conversion products were subjected to fractionation to form reflux condensate which was subjected to treatment, as aforementioned, to separate fractionated vapors having an end boiling point of 400 F. The fractionated vapors from this treatment were condensed and-the resulting distillate commingled with the fractionated vapors from the thermal cracking treatment and light rei-lux condensate, as aforementioned.

'I'he yield from this operation based on a feed of 50% reduced crude, and 50% gas-oil, was 60% of 300 end point gasoline having an'octane rating of 78, a bromine number of 8, and an octane rating of approximately 90 after the addition of 6 cc. of tetraethyl lead. In addition, approximately 20% of non-vaporous liquid residue was obtained having an A. P. I. gravity of 10, the balance being attributable to gas and loss.

I claim as my invention:

1. A hydrocarbon oil conversion process which comprises thermally cracking a heavy hydrocarbon oil, catalytically cracking a lighter hydrocarbon oil, separating a light reflux condensate heavier than gasoline from the vapors produced by the thermal cracking of said heavy oil, commingling said light reflux condensate and gasoline products of both said cracking treatments,

subjecting the resultant mixture to the action of a cracking catalyst at a temperature in the approximate range of 600 to 900 F. for a contact time adequate to effect a substantial transfer of hydrogen from said redux condensate to gasoline boiling olens present in said mixture, whereby to produce a more saturated gasoline, and recovering the more saturated gasoline thus produced.

2. A hydrocarbon oil conversion process whichl i mixture to the action of a cracking catalyst at a temperature in the approximate range of 600 to 900 F. for a contact time adequate to eiect a substantial transfer of hydrogen from said reux condensate to gasoline boiling olens present in said mixture, whereby toproduce a more saturated gasoline, and recovering the more saturated gasoline thus produced.

EDWIN H. MCGREW. 

